Compressor casing and stator assembly



2 sheets-5119"c 1 W. A. LEDWITH ETAL COMPRESSOR CASING AND STATORASSEMBLY Filed Feb. 6 1951 NOV- 1, 1955 w. A. LEDWITH :TAL 2,722,373

COMPRESSOR CASING AND STATOR ASSEMBLY Filed Feb. 6, 1951 2 Sheets-Sheet2 IIIlIllllIIlIl/lllll I' ,.lllfll "funn Y quill /e g@ L Q United StatesPatent O COMPRESSOR CASING AND sTAToR ASSEMBLY Walter A. Ledwith,Glastonbury, and Edgar C. Shoup, Jr., West Hartford, Conn., assignors toUnited Aircraft Corporation, East Hartford, Conn., a corporation ofDelaware Application February 6, 1951, Serial No. 209,556

9 Claims. (Cl. 230-133) This invention relates to a compressor andparticularly to the arrangement of the casing and the stator vanescarried by the casing in a multistage axial flow compressor.

Where weight is a serious problem, as in aircraft power plants, anannular casing with no longitudinal splits provides a lighterconstruction with the rows of stator vanes being assembled by insertionaxially into the casing. A feature of this invention is an annularcasing within which the rows of stator vanes may be positioned, with therows of vanes being split and the casing serving to hold the rows ofvanes in assembled relation. Another feature is the interposition ofspacer rings between adjacent rows of stator vanes for maintaining thespacing between the vanes and for locking the rows of vanes againstrotation within the casing. Another feature is the arrangement of thecasing such that its inner surface diminishes in diameter from one endto the other to facilitate the positioning of the casing over theassembled stator vanes and spacer rings.

One feature of the invention is an arrangement by which to secure theseveral rows of stator vanes against rotation Within the casing Withoutthe necessity for a securing means between the casing and each separaterow of vanes. Another feature is the attachment of one of a group ofrows of vanes to the casing and the provision of intenengaging lugs onthe other rows of the group to prevent relative rotation.

Other objects and advantages will be apparent from the specilication andclaims, and from the accompanying drawings which illustrate anembodiment of the invention.

Fig. l is a side elevation partly in section of the compressor casing.

Fig. 2 is a fragmentary sectional View on a larger scale of the sectiondelineated by the dotted lines of Fig. l.

Fig. 3 is a fragmentary sectional view substantially on line 3 3 of Fig.2.

Fig. 4 is a fragmentary developed View substantially on line 4-4 of Fig.2.

Fig. 5 is a fragmentary longitudinal sectional view of a modification.

The invention is shown in a multistage axial flow compressorconstruction in which the casing 2 is unsplit in a longitudinaldirection such that there is no need for bolting tlanges or the likethereby reducing the weight of this element. This construction alsopermits the contours of the casing to be produced by turning operations,to give accurate control of wall thickness. The casing may be made up ofa number of separate circumferentially continuous rings 2a and 2b, inwhich event the adjacent edges of the rings may have complementarylanges 4 and 6 (Fig. 2) by which the casing rings may be held togetheras by bolts 8. For piloting the adjacent casing rings it may beadvantageous to have one of the ilanges (flange 6 in the arrangementshown) provided with a cylindrical flange 10 at its periphery of such adimension as to receive and t closely around the peripheral surface ofthe 2 cooperating flange 4, thus piloting the ring 2a with respect toring 2b.

The casing preferably decreases in diameter from one end to the otherand the inner surface may be provided with a number of axially spacedpiloting surfaces 12 each of which is preferably smaller in diameterthan the adjacent piloting surface for ease of assembly as willhereinafter appear. As best shown in Fig. 2, the piloting surfaces 12are substantially cylindrical and they are joined` by sections havingfrusto-conical inner surfaces.

The casing supports spaced rows 14 of'stator vanes which when thecompressor is completely assembled alternate with cooperating rows vofmoving blades, not shown. The individual vanes making up any one of therows of vanes 14 are supported at their outer ends by a shroud ring 16which may be axially tapered or frustoconical and which, in thearrangement shown, is provided with openings 18 to receive theindividual shroud piece 20 on each individual vane. The shroud piecesmay be welded or brazed or otherwiser positively held in the shroud ring16. The inner ends of the vanes may be secured in position as by aninner shroud ring 22, Fig.V l.

For the purpose of maintaining the proper spacing between adjacent vaneshrouds, spacer rings 26 are positioned between adjacent shroud ringsand are preferably notched to form radially extending lugs at oppositeedges as at 28 and 30 to cooperate with similar notches 32 and 34 in theedges of the shroud rings. The spacer rings 26 and the adjacent shroudrings preferably have integral inter-engaging means in the form ofinterlocking detents 36, Fig. 4, which serve to prevent relativerotation between the spacer rings and the adjacent shroud rings. It willbe noted that the spacer rings have piloting surfaces 38 which may be onthe detents 36 and which engage the surfaces 12 to position the spacersaccurately within the casing. The surfaces 38 are preferably locatedadjacent to the edges of the spacer ring.

For the purpose of preventing rotation of the rows of vanes within thecasing, one of the centrally located spacer rings out of a group ofinterlocked spacer rings and shroud rings has /a radially extendingilange 42 which is positioned between the flanges 4 and 6 of the casingand is prevented from rotation with respect to the casing by the samebolts 8 that hold the casing rings together. The flange 42 is preferablylocated on the endmost ring of the group such 'that the clamping of theilange serves to hold the rings axially in position within the casing.Pilot surface 38 on the flange end of this spacer ring is shown aslocated on the periphery of ilange 42.

For ease of assembly of the casing and stator vane assemblies around thecompressor rotor it is desirable to have the shroud rings for the statorvanes split as shown so that the stator vanes may be positioned betweenadjacent rows of blades on a completely assembled rotor. Thus, inassembling the device, each of the stator rings in the form of 2 halvesis assembled around the rotor with the spacer rings appropriatelypositioned between adjacent shroud rings until at least one group, asabovel described, of inter-engaging spacer and shroud rings areassembled as, for example, the iirst three rows of stator vanes 14a,14b, and 14o` and the inter-engaging spacer rings 26a, 26h, and 26a.When these are in position around the rotor it will be apparent that thecasing ring 2a may then be positioned around the assembled structure bymovement from right to left in Fig. 1 until the radially projectingflange 42a on the spacer ring 26a is engaged with the radial ilange 6aon the casing ring. It will be apparent that the spaced pilotingsurfaces 12 on the casing ring engage the appropriate piloting surfaces38 on the spacer rings. In a similar manner the shroud rings and spacerrings enclosed within the casing ring 2b may be assembled around therotor and then the casing ring may be positioned in a manner similar tothat above described in connection with the casing ring 2a; final resultis a very light weight casing and stator vane assembly which issuiiiciently strong to withstand the loads applied to itand which alsopermits the rows of vanes to be split Without a correspondingsplit inthe supporting casing. The splits in adjacent vane rings may bestaggered circumferentially to eliminate any general plane offlexibility in the assembled structure. It may be further noted that nofastening means are provided between the casing and each individualshroud ring or space r ring since the inter-engaging lugs betweenadjacent shroud ringsV and spacer rings will function to preventrotation of the parts within the casing.

In the modification of Fig. 5' the interlockingdetents which align thespacersand shroud rings may be replaced by axial pins 44 which arereceived in bores 46 in the spacer 26 and other bores 48 in the shroudring 16. It will be obvious that these pins will transmit the torquebetween adjacent shroud rings and will also serve to pilot the shroudrings and spacers so that a group of Shroud rings and spacers may beassembled without any extraneous supporting means prior to thepositioning of the surrounding casing. Also in this modification, as inthe. arrangement of Figs. 1 4, a clearance surface is provided betweenthe piloting surface 12 on the casing andthe shroud ring 16such thatthespacer ringsare the piloting elements between the outer casing and theshroudl rings.

It is to be understood'that the invention is not limited to the specicembodiment herein illustrated and described, but may be usedin otherways without departure from its spirit as defined by the followingclaims.

We claim:

l. In a compressor construction, an annular casing the inner surface ofwhich decreases in diameter from one end to the other, axially spacedrows of vanes positioned within the casing, each row of vaneshaving ashroud ring engaging with and supporting the outer ends of a number ofthe vanes in the row, and spacer rings between axially adjacent shroudrings to maintain the required axial spacing between the rows of vanes,said spacer rings having piloting means thereon for engagement with theinner surfaces of the casing to maintain the concentricity of the spacerrings with respect to the casing, and said shroud rings and said spacerrings having interengaging piloting means to maintain concentricitybetween the spacer and shroud rings, a group of said spacer rings andshroud rings having inter-engaging means thereon by which to preventrelative rotation, and one of'the centrally located rings of said grouphaving a radially, extending tiange engaging with atlange of said casingand held against rotation relative thereto.

2. In a compressor construction, an annular casing the inner surface ofwhich decreases in diameter from one end to the other, one end of'thecasing having a radially extending attaching flange, axially spaced rowsof vanes positioned within the casingLeach row having a, shroud ringengaging with and supporting the outer ends, of, a number of the vanesin the row, and spacer rings between axially adjacent shroud rings tomaintain the required axial spacing between the rows of vanes, one ofsaid spacer rings having a radially extending ange projecting over andsecured to the attaching flangeon thecasing such that the spacer ring islocated axially within the casing and prevented from turning therein.

3. In a compressor construction, an annular casing the inner surface ofwhich decreases in diameter from one end to the other, one end of thecasing having a radially ex tending attaching flange, axially spacedrows ofvanes positioned within thecasing, each row havingl a shroud ringengaging with and supporting the outer ends of a num,n ber of the vanesin the row, and spacer rings between axially adjacent shroud rings tomaintain the required axial spacing between the rows of vanes, one ofsaid spacerr rings having aradially extending flange projecting Theoverand secured to the attaching flange on the casing suchthatl thev spacerringl is located axially within the casing and prevented from turningtherein, said spacer ring and a group of shroud rings and spacer ringsadjacent thereto having inter-engaging means thereon by which to preventrelative rotation.

4. In a compressor construction, an annular circumferentially continuouscasing the inner surface of which. decreases in diameter from one end tothe other, axially spaced rows of vanes positioned within the casing,each row having a shroud ring engaging with and supporting the outerends of a number ofthe vanes of the row, said shroud ring being splitlongitudinally, and spacer rings between axially adjacent shroud` ringsto` maintain the required axial spacing between the rows of vanes, saidspacer rings being circumferentially continuous and having pilotingmeans thereon for engagement with the inner surface of the casing tomaintain the concentricity of the spacer rings and the adjacent shroudrings with respect to the casing, said spacer rings and the adjacentshroud rings having inter-engaging notches by which to maintain theadjacent rings in concentricity with each other.

5'. In a compressor construction, a casing having a number of concentricspaced surfaces on the inside thereof, axially spaced rows of vaneswithin said` compressor, each row of vanes having a supporting shroudring to which the outer ends of the vanes of the row are rigidlysecured, and spacers between the shroud rings of axially adjacent rowsof vanes, said spacers having means thereonV for engagement with theconcentric surfaces on the casing for piloting the spacers and theshroud rings within the casing, said spacers and said shroud ringshaving inter-engaging detents to prevent relative rotation.

6. In a compressor construction, a casing having a number of concentricspaced surfaces on the inside thereof and also having a radial surfacethereon, axially spaced rows of vanes within said compressor, each rowof vanes having a supporting shroud ring to which the outer ends of thevanespof the row are rigidly secured, and spacers between the shroudrings of axially adjacent rows of vanes, said spacers having meansthereon for engagement with the concentric surfaces on the casing forpiloting the spacers and the shrouds within the casing, said spacers andsaidshroud rings having interengaging detents to prevent relativerotation, one of said spacers having a radially extending ange engagingwith the radial surface on, and attached to, the casing.

7. In a compressor construction, an annular casing` having a pluralityof axially spaced cylindrical inner surfaces, with each succeedingcylindrical inner surface of less diameter than the previous cylindricalinner surface and further having sections of frusto-conical innersurface joining adjacent cylindrical inner surfaces, axially spaced rowsof vanes positioned within the casing, each row of` vanes having afrusto-conical shroud ring engaging with and supporting the outer endsof a number of the vanes in the row, spacer rings located betweenaxially adjacent shroud rings to maintain the required axial spacingbetween the rows of vanes such that each shroud ring is positionedwithin one of said frusta-conical inner surfaces of said casing, each ofsaid shroud rings being of less outer diameter than the inner diameterof said frustoconical inner surface within which it ispositioned so thata substantial clearance exists therebetween, said` spacer rings havingpiloting means at each end for engagement with the cylindrical innersurfaces of the casing to maintain the concentricity of the spacer ringswith respect to the casing, means connecting said shroud rings and saidspacer rings to maintain concentricity and to transmit torque and toprevent relative rotation between the` spacer and shroud` rings, andinterlocking means joining said spacers and shroud rings with saidcasingto prevent relative rotation therebetween.

8. In a compressor construction, an, annular circumferentiallycontinuous casinghavinga pluralityfof. axially spaced cylindrical innersurfaces with each succeeding cylindrical inner surface of less diameterthan the previous cylindrical inner surface and further having sectionsof frusto-conical inner surface joining adjacent cylindrical innersurfaces, axially spaced rows of vanes positioned within the casing,each row having afrusto-conical shroud ring engaging with and supportingthe outer ends of the vanes of the row, said shroud ring being splitsubstantially diametrically, and spacer rings between axially adjacentshroud rings to maintain the required axial spacing between the rows ofvanes such that each shroud ring is positioned within one of saidfrusto-conical inner surfaces of said casing, each of said shroud ringsbeing of less outer diameter than the inner diameter of saidfrustoconical inner surface within which it is positioned so that asubstantial clearance exists therebetween, said spacer rings beingcircumferentially continuous and having piloting means for engagementwith the inner cylindrical surfaces of the casing to maintain theconcentricity of the spacer rings and means interlocking said spacerrings with said shroud rings to prevent relative rotation therebetweenand to maintain concentricity therebetween.

9. In a compressor construction, an annular circumferentially continuouscasing having a plurality of axially spaced cylindrical inner surfaceswith each succeeding cylindrical inner surface of less diameter than theprevious cylindrical inner surface and further having sections offrusto-conical inner surface joining adjacent cylindrical innersurfaces, axially spaced rows of vanes positioned within the casing,each row having a frusto-conical shroud ring engaging with andsupporting the outer ends of the vanes of the row, said shroud ringbeing split substantially diametrically, and spacer rings betweenaxially adjacent shroud rings to maintain the required axial spacingbetween the rows of vanes such that each shroud ring is positionedwithin one of said frusto-conical inner surfaces of said casing, each ofsaid shroud rings being of less outer diameter than the inner diameterof said frustoconical inner surface within which it is positioned sothat a substantial clearance exists therebetween, said spacer ringsbeing circumferentially continuous and having piloting means at each endengaging adjacent inner cylindrical surfaces of the casing to maintainthe concentricity of the spacer rings and means interlocking said spacerrings with said shroud rings tol prevent relative rotation therebetweenand to maintain concentricity therebetween, and interlocking meansjoining said spacers and shroud rings with said casing to preventrelative rotation therebetween.

References (lited in the file of this patent UNITED STATES PATENTS1,692,537 Baumann Nov. 20, 1928 2,434,935 Kroon Jan. 27, 1948 2,445,661Constant et al. `luly 20, 1948 2,488,867 Judson Nov. 22, 1949 FOREIGNPATENTS 233,643 Switzerland Nov. 16, 1944 586,562 Great Britain Mar. 24,1947 622,895 Great Britain May 9, 1949

